The invention relates to a method for heating the washing fluid for the windshield wiper system of vehicles and to a corresponding thermal windshield washer system.
It is an experimental fact that the effectiveness of a washing fluid is appreciably greater if the water is warm or even hot. This is also true of windshield washer systems of vehicles. An additional fact in the case of vehicles is that a thin ice layer forms on the windshield in the colder season. Where internal combustion engines are concerned, a great amount of excess heat is generated during operation, and this can be used, at least in winter, for heating the vehicle interior and for heating the washing fluid. Since the vehicle interior often does not require heating, however, separate line systems must be provided for both functions. Heating the washing water via the engine heat presupposes the internal combustion engine has been in operation for some time. During the cold starting of a vehicle, therefore, there is no heated washing water available, above all in the cold season. In order to device the vehicle windshield, the engine in each case has to be run in the idling mode for some time, until the washing water has reached a sufficient temperature. This results in air pollution.
It was proposed, in Swiss Patent, number 01 492/92-7, to improve this situation by providing to a washing system an additional thermal vessel, in which already heated washing water can be stored. It was assumed that, during travel, heating energy, in particular electric energy, is available in excess, so that it can be stored in a thermal vessel. The thermal vessel can be insulated relative to the outside in such a way that it remains warm, even overnight, so that a frozen windshield can be de-iced in the morning or at any time during the day while parked. It was possible for the functioning capacity of the thermal vessel to be proved by testing over a relatively long period of time. A disadvantage of this thermal vessel is its size, which means that the corresponding storage volume can be installed only on larger types of vehicle. The inventor, then, recognized, however, that all the solutions of the prior art took into account only some of the windshield washing problems. The winter problems were dealt with primarily. In the transitional period, but particularly when the roads are wet, not only dust from the road settles on the windshield, but regularly also a salty and/or oily coating. On dry summer days, there are dead midges which cannot easily be removed due to the protein. When the windshield wiper system is switched on, the entire windshield is often smeared, even though the washing water contains a chemical washing agent.